When to Use Handle Classes
Handle objects are useful in specialized circumstances where an object represents a
physical object such as a graph or an external device rather than a mathematical object
like a number or matrix. Handle objects are derivations of the handle class, which
provides functionality such as events and listeners, destructor method, and support for
dynamic properties.Use a handle class when:- No two instances of a class can have the same state, making it impossible to have
exact copies. For example:- A copy of a graphics object (such as a line) has a different position in its parents list
of children than the object from which it was copied. Therefore, the two objects are
not identical. - Nodes in lists or trees having specific connectivity to other nodes — no two nodes
can have the same connectivity.
- A copy of a graphics object (such as a line) has a different position in its parents list
- The class represents physical and unique objects like serial ports and printers.
- The class represents visible objects like graphics components.
- The class defines events and notifies listeners when an event occurs (notify is a
handle class method). - The class creates listeners by calling the handle class addlistener method.
- The class subclasses the dynamicprops class (a subclass of handle) so that
instances can define dynamic properties. - The class subclasses the matlab.mixin.SetGet class (a subclass of handle) so that
it can implement a graphics object style set/get interface to access property values. - You want to create a singleton class or a class in which you track the number of
instances from within the constructor. - Instances of a class cannot share state, such as nodes in a linked list.
See Also
Related Examples
- “Handle Compatible Classes” on page 12-39
7 Value or Handle Class — Which to Use